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urovEasrry oe fiojida 


I am pleasad to eatervd my sincere gracTtude to Dr. C. J. Wilcox 
for his lasting patience end understanding In planning, directing, 

Breteful acknowledgement Is eKpressed 

fine friendship and generous sharing of time and talent throughout 

whoalwy* iostillui wtttitn tns tt.« dosir. for koowlodge. Ttio corr- 
tinuous devotion end uoderscendlng of my wife, Luey, during tlie 
entire period of graduola iludy, and the Inspiration of my daughter. 



PravlQus Dry Pi 
Hartubtltcy , 




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<4 rcn ranged betueen 2,910 snd 3,872; 103 end I3li; end 2.893 end 
3,538 kg, respectively, nature cows averaged 68 ssontbs, 296, 175, 
and 98 days, for age, lengcb of record, days open, and previous dry 
period, respectively. Average milk yield for this group of cows 

age significantly affected yields of mature and all cows. Effects 

o meturl ty varied frc 
iffected production In all tnree groups of cows studied. Days open 
Ild not affect significantly milk production. Ho significant effect 

letacted. However, linear and quadratic affects were statistically 

herl tabi I i ty and repea tabi II ty estimates. Pooled berl tablll ties wi 

environmental correlations, assortetlve meting, and unusual differ: 
contributing to the wide varletlon and high henltabillty estimates 

climatic and management could be reasons to partially explain the 
vanlable results found for nepcatabl 1 1 ties. 

So« Il56 records from 203 deughters of SO different d.S.A.. 
Holland, and Colombian sires were considered in a study of herd by 

herd by sire significantly affected ml Ik, fat, and I|S FCrt yields 
with exception of sires on fat yield where no significant effect was 
detected. The widely divergent origin of sires and the large envl- 
ronmentel differences between herd locations partially explained 


hai brought a food defIcEc which is particularly acuco In tropical 
couritrlos, Two-thIrCs of the world's poopla live In countries with 

nutrl clonal ly Inadaguace diets. In order to maj ntain the! r onn 
Increase available food supplies three to 5) par year. 

Che sub-tropicel and tropical regions of the world. Hlllc from dairy 
cattle Is one of the possible sources of huioan food, It provides 
high quality proteins to a world In which a protein deficiency already 

iieately three tlaies this amount (3). Average milk Intake In Latin 
American countries is estimated to be around 8J.7 kg, while In Colombia 
It Is only 52.6 kg. This amsunc Is about one fourth of the consumption 

tional problems of people of tropical areas can be alleviated. In part, 
by Increasing milk production In these ercas and consaguencly Increas- 
ing the avallebllltv of protein per ceplta, 

affected not only by genetic potential , but also by environmental 

It is beilivBd that progress 

tropical countries. The sene Tack of 
sitlcudes of Colombia. 

cattle In Coloirftla, as In any 
Invosclgate the Influence of 

riod of 12 years In threo different regions 

ductlve performance ol 

^e dl fferenc cl I mat I e ci 


e ressordi published ci 

n gftnoreced In tropical end subtropical regloos. 

Itcproductiva efficiency often varies within and between herds 
without any apparent reason, lasses In breeding efficiency of dairy 

Factors that effact the length of the period froe one parturition 


Dunbar and Henderson (70) studied records of 1,015 Holstein cows In 
4 program of artificial Insemination (Al) In Hew York State, and 

30.000 Pennsylvania OHIA racoVds. 

ec al. (kk). The study was based on 355 parturitions In an outbred 

breeding cenditlon, (d) Infertile service, and (e) loss of pregnancy, 

21. S, and 11.5 days, respectively. 

An analysis of rho effect of month of calving un length of sub- 
sequent calving Interval was conducted by Poston at al. (152). Yhey 

from 397 to 622 days for calvings In October to May. respectively. 
Differences were significant (P «0.01) for months within year and 

studied the length of I ,782 ceiving Intervale of 

end 2,292 Intervofs of Black Plod Banish cows. Calving Inleryala 
averaged 394.0 and 380.5 days, respectively. Significant difforonces 
due to season of calving vrere afaserved. In both breeds cows ceiving 
In April had the shortest calving Interval. 

It has been shown that calving Interval as a measure of repro- 
ductive efficiency has a very low herltabl 1 1 ty. Dunbar and Henderson 
(70) indicated that solaction for fertility, measured by calving 
Interval , cannot bo very effective. The herl tabi 1 1 ty of tnl s trait 
In their study was estimated to ba sero. Legates (116) also found 
the narltablllty of calving Interval to be zero In a study of 1,016 
dairy cows from Horth Carolina. Horman and Thoele (142) Found that 
Intpa-berd herl tab! 1 1 ties ranged from 0.02 to 0.04, and Andersen 
(12) observed values of 0.012 and 0.056, respectively, for Red 

estimates of horltablllty for breeding efficiency have been found, 
Wilcox at el. (206) measured the reproductive performance in a 

bllUy of breading efficiency observed In this study wes 0.32. In 
beef cattle, Deesa (64) studied records from a purebred Brahman lierd 
and a crossbred foundation herd In Florida, Harl tabI 1 1 ty estinales 
for calving rate calculated by different methods ranged from 0,21 
10 0,63. 

The reproductive behavior of European dairy breeds subjected 
to tropical Bnvironment has boon in many casas disappointing. Tha 
lower reproductive performance of these breeds In the tropics, as 


lls of 531 t 27.0. 

efforts opoA cnc dlffarent phra’ologlcal processes. 

I.OflO calvings. Carnelro et a!. (51) found li 

(ISS) reporud an Interval of 1<65 * 38.2 days for Brovn Swiss cows 
under experlisenta] conditions at Karaeay, Venezuela. Carrona and 
Itunoz (50) analyzed 246 calvings of Jersey and crossbred Brown Swiss* 

of 384 and 413 days, respectively. Sl-Snolkh and E]-fou1y (74). 
studied 832 Intervals of frieslan cows In U.A.S, Tne avarogo lengths 
of Che first four calving Intervals were 474, 355, 352 and 344 days, 

Keproduccive perfornanca based on calving Intervals of soma 
native bi'eads In tropical areas has been reported. In most cases 

brands under tropical conditions, Hehadevan (123) studied Sinhala 
cattle In Ceylon and found an average calving interval of 355 days. 

Oe Alba ajtd Carrera (62) Indicated an Interval of 386.7 days for 
milking Criollo cows under conditions of Turrlalba, Costa Rica, 
Similar results with the semu breed were also found by Carmona and 
Hunoz (5C). Bodlsco et al, (35) studied the performance of milking 

(34) reported 415 t 3.0 days for U10 same typo of cows at Haracay, 

MS gosMCtoM sf KetKina 

Jersfly - 3/4 eOJ# eroasbre 
C^lvlna Tbte 

) r-eporEed esrvtna parlada gf 372 gnd 33 

cdlvlAg and ghorcei 

iltm (6) obaarved Ehac calving Intei 
interval was longer following tl 

class corrolaUgn was 
bl 1 1 cy and rapeacabll f 
respectively. For the 
reported herl tabi 1 1 Cy 1 

Calvtno Date to First I 

I -0.54; and repeatobi Titles 0.47, 0,40, 
respeatively.for Red SIndhI [two herds), 
and KankraJ cattle, A negative date- 
oond by Singh and Prasad (I76) for Intervale 
. The repeatability caleulated by Intra- 
^ ^ 0.053. Kusbweha {113) found berita- 

e type of cows, Johar and Taylor {lOI) 

pol ides of 

reported ]n e ainnmary of breeding failures In Washington that there 
r^as an apparent loproveisent in breading efficiency by welting at 
least 50 days after calving before breeding, 

Chapeun and Ceslde (Sb) found that the average interval froa 
calving to first heat in dairy cows was S9 t 39 days. In abnomel 

previously, the period was 71 days. 

Wisconsin and found the Interval from calving to first estrus to be 
69. b days for cows lallkod Four tiim per day, 71.8 days for nurse 

frequency oF suckling or handling oF the cents In milking mos 

I 3k7 dairy cews which had completed 
si perturl tTons. They found an avorage Intervel oF $7 ^ 28 

was longest, about 75 days. For first-celf helFers (1-1/2 
years), shortest, or about 50 to days, For co-s from 

Such ee a], (M*) reported an average Interval oF 33 days Prom 
322 normal calvings oF Holstein cows In Wisconsin, They found that 
cows calving during suimnsr tended to cone In heat earlier (28 days) 
than thoso calving In the other seasons (3h days), whereas those 
calving during winter had the longest Intervals (38 days) From 
parturition to first heat. Such et al. (I13) found that the Interval 

this Inicrvnl was influenced significantly hy age of the cow, being 
h2 days In primiparous and 50 days In plunlpanous. Also, slgnl FIcant 

positlan, tonus and size. Similar 1 

Intervals from calving to first heat of IS.O days after normal calvings 

t (9*.) s 

Is From Garnao Spotted Mountain 
od tkecwean celvlns sod First 

cattle, end Indicated that the p 

Fluonced by heredity. Herlteblllty values near eero uere reported 

Ke found Man lensth of calving Intervols to first heat of 55.1. and 
71.0 days, with repeetafal 1 1cy eaclieeted to be 0,15 end 0, 27, rcspec> 
lively. On tho other hand, her! tabi 1 1 ties of 0.J7 and 0.32 were 
roportod by Olds and Seath tlbS). They based these estTmates on 
the InCrasIro regression of daughter on dam using the first available 

that the relatively flMd physiological characteristics determining 
tho Interval from oalving to first heat In Individuals seeaed to be 

lactations from the Itentueky Enperinent Station dairy herd. 

Season oF calving had o significant eFFoct. Intervals of go.lil*, 

spring, suiisnar, and fall, respectively. Hies f I Iho and Costa 
Aroeira (136) reported a mean Interval of 87 days obtained from 75 
Glr dairy cows In Dresll. Follon (75) investigated 383 Jersey cows 

parturition and first heat was Ii0.t<5 t 22.70 days. He Indicated chat 
Fertl II ty at first heat was a function of Iho postpartum interval 

Influonca tli« Unstti of the service period, Chapman and Casida (5I1) 
the service period was ISO days, of which 50 days was the period from 

first Ser vice to eoncemlon 

Chapman and Casida (5h) studied the lerpth of interval from 

from Wisconsin and foued an Interval of 30 days. Tabler ot al. (186) 
analyzed 15 cow families of Che Ayrshire breed end observed an 
avereje of 69 days. He also reported a preator variation within 
families than between families, and sipnificant differences due to 
sire effects. Pou ot al. (153) found a man interval of 5? days 

age of the cow had little effect on the number ef days to conception, 
CoQpor ot el, (58) enaiyzed 6,196 calvings from Kentucky DHIA herds, 

concaptlen occeuntod for 61% of tho variation in calvihg Interval. 
RepeatablUty and herltehllity values for breoding efficlohcy 

estimated by Pou et al. (153). They used the val 

ind daugnt9r>dacn cross-products for Keri tab! 1 1 tics. Values obtained 
vare O.ll and G.07, respoctivaty. Smaller repeatability and herlte- 
>ilrty values wero reported by Carman {If8). Based on tbc estimates 
>f components of variance, and utIUzIns data Prom the How York 

il Breeders, Ounbar and Henderson E70) reported repeetablUty 
.0 first service to be 0,027. HerltablllCy of non 

Sqrulces per Coneentlon 

as a measure of breedlns afplclency. 

cepUon In herds free of disease ere fertility of the 
of the coe, age of the cow, cUmetologlcal conditions, 

tamperete countries. Boyd et a1. (39] analyzed 29 her 
by Che Kentucky Artificial Breedln 9 Association, and f 

Tnvestigacad cho brooding efficiency of 

0,74. Carman £48) 

tlvely, Tanaba and Salisbury (167) studied 12, 

Ing officlency of 46,2S£, VonDemark end Salisbury (194) studied 
I.B74 pregnancies of cows from tbe University of Illinois dairy 
and Indicated Chat 1.97 services per conception were reciulred. 

Legates (116) scedied 1,129 records fropi 12 North Carotloa herds, 

Legeces (H6] to be 0,026. He concluded that the number of services 
required per conception for one calving Is of rro value In predicting 

nancy. Carman (M) reported values of hcricabinty and repaetabl 1 1 ty 
close to aero. Also, very Mule genetic variability In services per 
conception was found by ocher Investigators such as Trlii*erger and 
Oavls (191), Olds at al. [iMi], and Tablor ec al. (186). 

Howsvep, Serga (29) studied data of the Norwegian Agricolturol 
College herd, and found that tha ropaa cab 1 1 1 ty of conception rates 

Singh (179) studied deco on 687 calvings of Tharparkar cows, 
and found that Che number of services per concopcion was 1,76 ? O.OL6. 

a (Ii9) raported 9,8h t 0.6} services 
') obssrved services per eonespcion 

SRperlmencel station In Colondsla, 

second pare Into which calving Inearval Is 
caccle, several InvesLIgatlons have been ti 

Keen gescetlon lengths of different br 
svimarlzed fay Andersen and ?Iiun (13). Hear 
for Holstelns Co 29D.9 days for arown Swiss 
length of Holstein cattle from temperate co 

Is of dairy cattle were 
The mean gestation 

n tropical e 

0.19 days as reported by During (I 
Destatlon periods of Holstelr 
studied by Velga ec al. (I98) who found 276 1 0.39 days for holsceli 
Friesian cows in Sraall. similar results wore observed by Grossman 

Deasoulty and Reiika (66) studied the gestation period of Friesian 
cattle In Egypt and found an average of 282.3 t ID.30 days. Ward 
and Castle (202), based on 2,228 gestations of dairy cattle in How 

Studies of various native breeds from tropical areas have been 
reported and In general It has been observed chat the duration of 
their gestation periods was longer than chose observed In cattle 
from temperate countries. Jordeo and Velga (104) studied 980 gesta- 
tlone of Caracu cows In Brazil and found an average gesteclon period 
of 286.9 t 0.35 days. Joubort and Bonsma (106) reported 295.0 t 0.3 
Rageb and Asker (155) reported 289.5 t 7. 

^url (HI] obsarvod average 

geeCatloe period of 290.7 t 0.90 In Harlan cattle from Indie. 

Mlnter months earrlad their calves an average of orva to three days 

the Sumner ware observed by Alexander (5) from a study with dairy 
breeds In Illinois. Joubsrt (105) Indicated that prognaneles of 

calving on length of gestation In Egyptian cattle. Chaudhurl and 

on gestation length In the study carried out fay Kohll and Surl [III) 

However, several Invastlgacors have reported that season of the 

affected by seasonal differences according to folllns et al, (162) 

In their study of Inbred Jersey cows In the University of California 
herd. Lazarus and AnantakTshnan (115) did not find any signi f leant 
Influonco of month of calving on gestation length of Indian cattle, 
Similar rasults were roported by Desseuky and Aakka (66) for Frlaslan 

The ofFoct of sire on gesrstlon period has beon studied by var- 
ious euthors. Some hove Indicotod Chat service sire hed on InFlucnce 
on gastdtlon longth,' Analysis of 1.82A gestation periods of Kolstein 
cows from Washington was made by Knott (109), da observed that 
gestation periods of calves sired by soiaa bulls were definitely longer 
or shorter than average, and Indicated the possibility of paternal 
Influence, Also. Alexander (5) Indicated that sire affected length 

dairy breeds, Brakal et el. (bO) comparod mean gestetlon lengths 
resulting from the use of different sires and Found significant Inter- 
sire differences In Holstein, Jersey and Ayrshire breeds, Slgnlfleant 

td 85s cslvlngs of Egyptian cc 

IS9 calvings of Dairy Shorthorn cows and found that sirs of the calf 
had a significant effect on gestation period, Similar results were 

with 180 Egyptian cows. Significant differences were also reported 
by Kohll and Surl (III) In their study of 797 gestations of llarlana 

have e slgnirieant effect on the cow's gestetlon period, Their study 
was basod on 827 gestations of pure and crossbred Africander cows, 

gsstatlon appeared not to be Influenced significantly by sire. Their 
study was based on records of 2IQ Zobu cows from Breall, 

Several rasearcliors have Indicated that age of dam affected the 

the Ohio Scats University pursbred dairy hard. Tbay observed that 

: covs, eonpared Co < 
lelfers. Seal loop ei 

al. (IB!) Investigated gc 

. calf heifers Mere Fovnd by Uilcox and SteFFa (20B) in 
:l dairy ceccle at Florida Experimental station, They 
I Chat age of dam might Influence birth weights and gestation 

Copeland (SSj studied 1.075 gestations oF Uersoy cows In Mew York. 
oF I, job normal parfuriclons of Jersey cows (First calf heifers omitted) 

sIsnlfTcanC effects of ege of dan on gesteejoo length of Therperkat 
caws Tn India, Also, Joubert and flonsma (lOb) reported no effect 

by weight of dan, Ft 
Wisconsin Holstein ec 

1 at al. I&2) toported a positive correlation 

Anantakrishnen et al, (II) and Kohll and Surl (111) In their study 
with Indian cattle, and by Ahimd and Tantawy (b) with Egyptian cows. 
However, Vukavlc (200) working with Slranental and Hakela and Olttlla 
(129) with Ayrshire cattle did not find any correlation batwdon 

records from the Missouri Stotlon hard, and foond that Che average 

(ho) I, 

significant dlfferancQS wore also observed by b> 

In thoir study of flairy Shorthorn cows In England. They found that 

1.68 days, hnlllns at al. (ISJ) analyeed records of 1,353 gestation 
periods of Inbred Jersey cows from the University of California herd. 
They found that nelo calves wore carried In utero 2 days longer than 
fomata calves, This difference was highly significant. The effect 
of sea of calf was also found statistically significant by doFrles 
et al. (65) with data representing the five major dairy breeds frem 
the Uhlvertity of Illinois herd. In general, male calves were carried 

has no Influence on gestatlo 
755 gestetlohs of Holstein co. 

They found chat length of ge< 

for females 278,6 days, Alst 
gestation length of frleslan 
affected by sex of calf. Avc 
and 281.85 t 76.38 days were 
respectively. Singh 

gasieclon period was 289 t D.66 
females, The average gestation 
Friaslan calves observed by Jume and Xassir (] 
ond 276.8 days, respectively. However, 278.6 
and femolc crossbred Friesian (mainly 7/8 and 

s from Che University of Nebreske herd. 

sn length for malas was 278.5 days and 
Cessouky and Rakka (66) observed chat 
ittle In Egypt was statistically un- 
ige gestation lengths of 283.83 t 13.22 

(I//) with Tharparkar ci 

d 276,9 days fo 

of o.w. 

ig Ifttit pi-«ccleal slgnlfUanca. He finally 
n- tentrolling variations in the calving 

61 rth tfctohi 

6lrch weights of dairy calves have been studied by several 
authors from temperate countries as well as front tropical ones. 

of 755 gestations of Hoisuin cows from the University of Hebraska 
leant Influence upon birth weight of the coif. Stone ec al. (182) 

L«gauU and Touchberry E1I8) Si 

!d 1,234 birth weights represertt- 
cettle from the University of 

HcCendllsn (134) studied 369 

ege up to 3 yosrs, the everege bln 

Asker end Itegeb (20) In e study corrlod out with Egyptlen cettle 
slgnlflcent differences between birth weights of eslves. Seoie Influence 

significantly correlated with birth weight of purebreds (0,99) end 


ond De faula Aasis (103) of data Eakon from Hause-Ahlne-yssol caEtle 

were scudtad by KohH and Surl (111). They did noE Find any algnjf* 

al. (30) found also ThaE bIrEh weight of Sehlwel calves was not 
significantly correlated with age of Che dam. 

That the weight oF the dam has a positive correlation with tha 
birth weight oF the calves has bean confirmed by several researchers. 
Correlations of 0,13 ond Q.hl have been reported by Hakela and Olttllo 
(1 29) , and Anantakrishnan at al , (II), respectively. In their studies 

little or no effect on birth weight of calves. Tyler at al. (192) 
studied birch weights of offspring of six Holstelo sires In two 
Wisconsin herds. They did not find any significant differences be- 
tween years or seasons. Similar results ware reported by Hartin (1)2) 
who studied 659 dairy calves from chs lows State Collega dairy herd. 

Asker and Ragab (20) Indicated that month of calving appeared to 

signi flcencly effected 

bred rrleslan caivss sCudled by Judia and Flassfr (107). Winter-born 
calves averaged 34,1 kg wbcroaa 32,3, 26.3, and 33.3 kg were observed 

a is a general agraamont that male c. 

indicated a range In birth weights fron 92.3 to 101.0 ib for naies and 
from 85,3 to 94,0 Ib For females. In an early atody, Eekles (72) 
reported upon 433 talf weights obtained from the dairy herd at the 
University of KIssourl. he staled that male calves averaged from 
S to ^ heavier than Females, HcCandiish (134) suetnarlxed 369 calf 
weights from the Iowa Stata College delry herd, hale celves averaged 

than Famalc cnlvas. The average weight of all bull calves studied 
was 7.8X heavier than females, Tyler et al. (192) studied 794 
Holstein calves in three unrelated hards from Wisconsin. They In- 

scudy of 759 Holstain calvss born at the Unlvarslty of Nobraska, Davis 

significant at tha 1% lavel, Foote at al. (82) In thair study of 
938 gestations of 258 Holstein cows found chat male celves averaged 
9.92 Ib heavier at birth chan Females. Legault end Touchberry (118) 

analyzeif data from tho University of Illinois dairy lierd consistina 
of 1,234 birth uoights representing tlie five major dairy breeds. 
They found also that bull calves were significantly heavier than 

Average birth weights 

Shelia et al. (30). Beckh 

hathout (25) reported birth weights 
Female frteslan calves, respectively, 

On the ocher hand, birth weights of IJ3 pure and 82 crossbred 
Friesian calves wore studied by Junta end Kossir (10?] In India, 

They found that the weight of calves was not significantly affected 
by sex. Average weight for males vies 32.41 kg, while femalo calves 

found a highly signifl' 

It posIcTve correlation 

relationship between itean 

6ronn Swiss, Gjernsay, Ayrshire and Jersey calves. Davis et a], (6D) 

studied 755 normal gestations of Holstein calves and found that the 
correlation between gestation length and birth weight was 0.26. The 
regression of birth weight on gestation length was 0.66 lb per day. 
DeFrles et al. (65) studied 2,053 gestations representing the five 
major dairy breeds. The observed correlations between birth weight 
and gestation length were 0,1(7, 0.3b, 0.34, 0.37 and 0.12, respectively, 
for Holstein, Brown Swiss, Cuernsey, Ayrshire, and Jersey, Regression 

of birth weight on the length of -the gestation period Indicated that 
calves carried one day less than average era approximately I !b 

Ragib end Asker (154) found that there was a positive correlation 
(0.316) between gestation period and birth weight of 055 calves from 
Egyptian cows, Also, Ahmed and Tantawy (4) found highly significant 
correlations In another study with Egyptian cattle. 

repea tebi I Ity 

0.38. 0.1 

trouble, sterility, abortion entf deeth, respectively. Based on 7,36r 
cows Prom New Pork herds, O'Bleness and Von Vieck (Ik3] reported the 
most important reasons for dispusal to be low production, 27-3R; 
sterility, Ib-IKl udder trouble or mastitis, 14-21^ and sold For 
dairy purposes, I4-I5X. White and Nichols (205) studied data Prom 
1,34? Holstein cows In Pennsylvanto herds end found that the main 
reasohs for disposal were: low production, sterility, udder trouble, 

13.5 and 7.9, respectively. 

On the contrary. In a comparison with the above mentioned studies, 
Parker et al. (147) analyied a special herd where no animals were culle 
. Seasons for disposal of Holstein and Jerseys were 
:at 41.3% of the Holstelns and 21.3% of the Jerseys 

n nas ].8X. Fie reported a percentage of 

e low milk production oF natlvo cows and increasing demand 
k initiated the introduction oF some European dairy breeds 

the opportunity of studying responses oF pure eaotic 

of greding-up native cattle with those European breeds. 

regions has been explained by the 
cattle In tropical a 

•ate countries. The unsatisfactory 
IS low plane of nutrition, diseases, 

e pertaining to performance oF 
s shows that average mllic yield 

1 kept at experimental stations and governmontel 
and 2,300 kg reported by Karvaax (IbO] and 
IS carried out In Panama and Bratll, respectively, 

Schindler (93) from observations tokon In Ceylon and Israel, respec- 

I. (163) 

testTn^ progr«oi of Che Ecuodgrlan Holscein Associatian, Sooie 45,000 
records grouped in four areas renging froei 2,250 to 3,100 iMters in 

yields varied from 3,803 and 128 leg to 3.564 end 142 kg, respeetively. 
Weils et a). (203) from a smeH eaperireencal herd situated at an 
el cl Code of 2,000 loacers In Ethiopia reported an average of 4,583 kg 

The highest notional ml Ik production 

with Che 1566-67, D8IA (67) Holstein cows 
produced an average of 5,800 kg of milk an 

and enuironnente] . For purposes'of selection and Preedlng, It is 
Important to make accurate al ]ov*ence for the one In order to arrive 

at a good estimate of the other. 

Leaving aside the variation due 

affecting milk yield. Among them are 

record, days open, and previous dry period. 

Host studies carried out In temperate as well as in tropical 
zones Indicated tnat year of calving exerted considerable influence 
on variation of milk yield. This variation Is iofluencad by the 
Improvetwnt of nutritional and managerial conditions that from year 
Co year are practiced In many herds. However, the use of soleccion 
of Improvod animals end culling systems affects also this variation. 

The lISDA (153) reported on Increase In overage milk yield from 


States is i «hale, A good eiimpTe of long-term year influence Is 
TIM oignlf leant effect on milk yield Indicated by Wilcox and Young 
(209] In a population of Jersey cattle under the seml-tropleal 

are considerable. A hnculedge of the magnitude of yarlatlon according 

Extensive observations concerning tlie effect of montb of calving 
been carried out In temperate 

.tries. Woodward (210) found 

calving In herds at 

' sllglitly different [r 

calving on milk production Is available from tropical countries. 
However, Clark ($7], from a large volume of data on dairy cows In 

(lueenslami, Aiistrsl'a, publlsKsd in extensive sliidy covering the 
period 191*8 to I960. He observed thet deiry cows Chet freshened In 
June end July produced 2014 more milk end butterfet then those which 
celved In Deceidier, Jenuery or Februery. He elso Indlceted thet 

tions then chose which celved during other periods. Simtier results 
were reported by heufel fibl) who enelyeed 1,595 leccetions of 

cows calving In fall and winter produced sign! floetl vely more nflk 

highly significant differences In dally milk yield of Crlollo dairy 

Conflicting results have been reported by other investigators In 
tropical lones. Hehadevan (125) observed that the variation in yield 
with month of calving was not significant In his study of European 
breeds, Including HolsteTns In Ceylon, eoyazoglu (37) In study of 
ebout 20,090 records of frleslen cows In South Africa Indicated that 
season of calving was found to be less Iteportant as a source of 
variation In milk and fat yield than Is generally accepted. Verde 
(199) observed variable results In his study with pure and cross- 
bred Holstelns In Venezuela. Hagofke and Bodlsco (I2l) also found 
that tnonch of calving did not Influence lactation yields of Criollo 
dairy cows In Venezuela. In support of these results are the findings 

factors effecting nl Ik yield 

fo European dairy breeds In Ceylon wes 

probably due to the late age at first calving (lu) months) and the 
Tong calving Intervals (ti6fi days) these animals showed. Boyasogtu 
ec al, (38) observed that manltnuffl milk production In Holstein cons 

The rate of Increose In yield from first lactation to maturity 
Is gererally larger In European cattle under temperate conditions 
than those subjected to tropical .conditions, However, there are 
several studies In which Intensively selected European breeds under 
good ntanagarlal practices In the tropics have shown Increases which 
ai'e contparable with those obtained In temperate areas, rtehadcvan 

creased with age, Thoaa Indreasas vorlad from 19 to 3iS and were 
considered to be similar to these obtained In Europe. AbdnI-QhanI 
and rahmy (I) from study of Holstein cows In Egypt reported an In- 
crease from first to fifth lactotlon of 27H. Also, Bodlsco at al. 
(33) studying performance of grown Swiss cows under the conditions 

0 Che ego of approxfoiDtely el 
he else foood that milk yield 

The average age at firac celvlnj for Hoi 
countries varies from 27 eonths as reported by Plum and Lush (151), 
to Jh leonlhi observed by Toymls (ISO), Salisbury and VanOemark (168) 
presented sunmary of date on age at first calving of dairy breeds as 
reporcad in England, Stidden. and United States. Mean age varied from 
27 to 33 months. Average age at last calving ranged from 59 months 

. (77). 

s (205) t< 

tropical environments hav. 

B under exparlmenta] 

it calving 

f 3U months. 

In halsceln covs under oaperlmsntel conditions of Egypt, Similar 
results uoro observed by Asker at al. (19) from study In Irak. 
Soyeaoglu at al. (33) from data on 3,000 registered elite friasland 
anvs representing 256 hards In South Africa found that age at First 
calving was 32 loanths. However, Kahadevan (125) In his study of 

f the purposes of standardizing 

t use of aga correction Factors Is 

correction Factors has been obtained From European breeds In temperate 

Factors for aga published For European broods to convert first 
lactations to maturity In tropical cattle. He stated tnat correction 
factors based on European data, when applied to Zebu stocic, would 

dicated also that It might even be wiser, as Robertson (ISO) has 
pointed out, to use no age eorreolton at all on tropical cettle than 

countries are presented In most of animal breeding and nanagement 

on perlodsas 

under tropical 


Tn Egypt, Arabian Rapublics, and Uganda »ere repartati by El-ltrlby 
end Aiker {73). Asker at al. (18) and Marptes and Trail (131). 
respeecivaly. Asker et al. (19) else fannd an average of 322 days 
for Holstein cows In Irap, and Boyazoglu (37) observed lactation 

by Pearson at al , (IAS) , to 317 days Pad SIndhI c 
a higb correlation between total yield and lactal 

tropics Indicate 

and Naidii and Oesal (138), respectively. 

parturition can be defined as days open. This variable Is Iruporcant 

Rice ec al, (158) concluded tbat with an average of 100 days 
open a 12 CO 13 nontb calving Interval would be maintained, SmI cH 
and Legates (178) In a study of nine North Carolina herds reported 

I, (102). 

or Tater, «nd all lactation!, rospiactivaly, Jc^naon ec al 
by describing tbe use of Herd neproducEive Scacus rnetbod end its 

year and to 11b days in tbs second year, darrancee (22) In a study 

end cows were I76 and ]fi2 days, respectively, and about 62% of 
particularly after I50 days of gestation. This variable (nay be 

finally concluded that, even In extrenely w«n-menaged herds, days 

open and 90~day and 3Q5-day production using b,385 lactation records 
from g Korth Carolina Institutional Herds, Relationships were studied 

end b.2% of the varletlon in 305'day milk yield for first, second or 

yosr old CONS, Spsldlng (180) Indicated correlations between days 
open and ml Ik yield to be 0,2Z and 0. 20, respect I yely, He also 
observed that 100 days opan compared with 6k days es standard incr 

Ho reported Inromatlon concerned with the effects of days open 
on milk yield of cattle under tropical condl tlona was available In 

Provlous Dry Period 

lactation and the beginning of the nest (the one being studied) 1$ 
celled previous dry period. 

:l (loo) In Swedish dairy breeds, 
al' (1S8), the number of days dry 

to colving does not greatly Influence li 
I period Is quite short, e,g. ,)0 deys oi 

kg, 169) have Indicated that 
'Up of about 15,000 lactations roprosencing 12 states la 
ntb. Spalding (180) found that a 50-day dry period wei 

cosqtorod wl tn 

( 183 ) 

periods produced 26% less 1|S fCK in the second 
iMtes which had a 60>day dry period. 

callTo. preuloua dry periods varying from 94 i 
reported from studies with Holstain cattle undr 
regions. El-ltrlby end Asker (73) reported an 
for Holstein cohs in Egypt, Narvaec (140) four 

ose found in temperate 

Egypt, end Hahadevan (125) indicated an average ■ 
periods of European dairy cattle In Ceylon. Puri 
Vonaauela had a previous dry period of 141 days . 
(199). Ho found no slgnlflcanc effeci of prevloi 
milk yield In a mixed population of cattle In Ve, 
Also, differences in lengths of dry periods 

varied from 116 days observed by Ha 
of milking Criollo cows In Costa RIc 

condi tlons of 

-a largely attributable to differences li 

Some ceoses of variation In milk yield di 
effects have been menclonod already, 
onvlronmontal effects, It Is apparent chat milk prodiietlon Is a 
hl9hly modifiable trait, Honever, In the study of causes of variation 
In milk production, senetlc effects must also be considered. 

The raletive effect of enyfrenment and heredity on the variation 
In milk production can be estimated by using adequate st 

estimating herl tabll I ties In order that Che breeder can make better 
use of selection systems In the Improvaimnt of characters of economic 

Johansson and kendel (100) sunmarlsed the results of herUabllity 

different breeds. They Indicated that. In general, practically the 
sano value of herltabITIty Is obtained by using butterfat yield as 
milk yield mhen based on compareble records, usually tbo first 305 
days of the lactation. Values of horl cebi 1 1 ties for ml Ik or but tor fat 
yield vary from 9.17 In Oulch Frlaslans to Q.hJ In six British dairy 

as found by Tabler and Touehberry (IBs). However, a nigh value of 
horltabinty of 0.76 was reported by Sur" Yanava (BS) from study of 

tatlons reported relatively high herltablllty values averog- 


hypotheses wore formulated. 

thereby Irifleted to a eertafo extern 
' heritabinty figures Here higher ai 

It was also explained that 
the testing stations than on the farms dui 
cleney In recording and bettor adjusticent 
Individual nutriont requirements, and partly due to thi 
nelty within and between groups at the same station 

Biased estimates of herlcabTlity resulting from It 

Farthing and Steele (80). They give an example by usir 
methods of atialyaing data of milk yield, and concluded 
which Includes sire, dam/sIre, 

tf her I lafal 1 1 ty of ml Ik yield for European end native 
en conducted In tropical environments, fiahadovan (I2fi) 
one of the main objects in estimating the nerltabillty 
in a tropical environirent as distinct from a temperate 

the character is different In the two environments, He also Indicated 
chat studies of the hariiablirty of milk yield at different environ- 
mental levels within tempenete countries have been quite contradictory. 
Studies by Johensson (gB), Korman (112), and Sravarc (85) raporiad 
herl tabl 1 1 ties to ba higher in high producing than in low producing 

(86), Burnside and Fannie (bB) and Van Vlaek and Bradford (Ig6), no 

^ Increase tn production 

Increaso In herltablUcy was observe 
level. Maharfevan (126) concluded that It may be chat very extreme 
environmental differences are necessary before they affect herlta* 
blllly. Ha also stated that unfortunately herltablHty studies 

Herltabllity values for ml Ik yield estimated from native breads 
ndar tropical conditions have been reported to vary from Q fj for 

tserved in mllklnp Crlollo cattle in Veneauela Indicated by fiagofke 

Estimates of herltabllity for milk yield from purebred European 

irved by Hahadevan (125) in Ceylon to 0.55 reported by Haufel (141) 
om a study of Holstein cattle in Srael I , 

A number of studies on herltabllity of milk yield In crossbred 

23, 0,19 and 0,21 ,vere Indicated by Okumu and Barry (145), SIngb 

I (174). Ht 

. raspactlvely, from 

te correlation between performance in different lactations oi 
fo animal, often given the name of repoatabi Ti ty , Is one of i 

ability refers to the average correlations over a series of 

artd can considered as the proportion oP efta total variance due to 
difFerences between cows which persist over ail lactacTons concerned, 
Estimates of repea tobi 1 1 ty For Holstelns under teirparate eondl- 

10 0.52 as Indicated by Oeaton end ncSMIlerd 
of records onprassed as deviatlorts from herd-y 
were reported by Beraskln and Freeman (27) to 

nepeaiebl II ties 

study of crosses between European and Indian breeds. 

AepcatabI II ty studies of European dairy cattle In tropical con- 
ditions hove varlod from 0.31 found by degofka and Bodlsco (Ul) In 
Brown Swiss cows in Venecuelo, to 0,65 reported by Kofomyar and 
Doyatoglu (95) In Jersey cows In South Africa. Kaufei (141) obtained 

•n value of 0,36 for milk yield and 0,4l for fat yield in Xolsloln cows 
In Brazil, Seller et al. (I?9) reported that repeatability astimatos 


I.72B Friesian 

was only 2* for silllisnd fat yield. Legetes at al. (II?) analyted 
production records of 25.00Q daughters of Guernsey, Holstein end 
(sed In artificial breeding associations throughout 

zero for Guernseys and Jersey and 2,1 end 1,21 for Holstelns. From 
results obtained In this study they finally stated that speelfic 
slits by herd differences were not of major Importance end that the 
ranking of a group of bulls based on their deughters' performenae In 
a given herd would be eapectod to be subs tantlel ly tha same as for 

herds In ths same steta. Hason and Robertson (133) studied milk 
records from 13,000 cows brad artificially In Denmark with herds 
divided into tnree groups according to production. They did not 

value was apparently cht 

jc ranking of bulls for breeding 

id at Danish bull casting 
ec al, (ICg) Indicated that 

with daughtors of Holstein, Jersai 
artificial end natural breading li 

Ively) Indfcoting little genetic by 
recorb! under New York condltTon*. 

practice] In 
Surdick end 
I Cuerncey be 

d (bs] tron o study of Hlchlgen 

greuped according 
slgniricant interaction Involving sire prool 
feeding In Sdnenor was found, suggesting tbai 
on the basis of progeny fed relatively nigb 

Burnside (130) found no Interaction of 
>reofs and herd environtrents when liards were 
factors, However, a blgbly 

Correlations between sire eyeluotlons at different herdmete 
levels have been studied by several Investigators, In most studies 

tend to rank slmllerly under different herd environments, Robertson 
et al. OSl) studied data from England, wales and Seottand. Estimated 
correlations betwean breeding values for yield et three levels of 

production were close 

prodactng herds and th. 
of level of production 
correlations In this s 

concluded fi'oei the 
progeny Lestlrsg Ir 



(05) TnvesiOfltod rolattomhips beteoen Independent nteesures ef 
the breeding value of a bull at different levels of herd production. 

contrary evidence has been presented by Sereskin and Lush (24) 
who Indicated that sdimnarlas on bulls In high level herds might not 

With the purpose of investigating whether genotype by region 
Interactions were important In ranking bulls, Lytton and Legates 

sired daughters of W Holstein sires used in the northern and 
southern regions of United States, Correlations between the average 
breeding values of sires in the two regions for milk, fet yield and 
Fat test approached 1.00. Eitlmetes of sire by region Interaction 

3 with a particular raglon should 


Oascrlptlon of tlie Herds 

Records of Kolstotn cows frosi three herds, belonging to the 
Colonblan Agricultural Institute (ICA), for the period 195S>I9§7, 

Colombian Holstein caitli, and of Holstein groups Imported either 
from Holland (Herd I), or from dflited States. Soma Importations of 
heifers from United States have been made In morn recent years. 
Purchases of semen from proved sires from United States have been 

The three herds are locatad at three enparlioontal stations 
situated In distinctly differont climatic and topographic conditions 
of Colotnbta, Table 1 shows somo details of the situation and pravall- 

Statluns I and 3 era si tuated ot high alt I tudes but wi th different 
topographic condltlohs. Statloh I Is on a plateau callaH Sabana do 
BuguLa, whiuli la located at the Centre! part of Colombia, Tha land 
it cOimplBtely arable with highly favorable el Imatic condl tlons for 

sTIaga, Pastures prevailing in the station are Kikuyu f PonIsetum 
elaodastinum). Ryegrass (Lollum nerenna l. Drehard gross (Oac lulls 


Toblt I. STtuatlgn and cIlMtlc conditfons gf the three 

Average Relative Humidity 

Statign I Station 2 Ststlon 3 

(Herd I) {Herd 2) (Herd 3) 


76° 17' W. 
B7S.3 rm 




permitted. Furtheritore, all milklnj animals 
accordlns to production. The principal 

Seconds In this study were divided In two different groups. One 
roup consisted of information related with reproductive performance, 
ne second group concerned with milk production of the three herds, 

tis data, and records with celvfng Intervals longer than 730 days 
id gestation lengths shorter chan 230 days were ellmlneted. 

Production data consisted of 2X. 305-days, or less, complete 

(2) Animal numhar. 

(5) greed of sT re, 
(6} Oem number. 

SI rth date. 

(IQ) DaCA of last parturltfon. 
(II) Data or first haat. 

(13) Data of conoepclon. 

(Il*) Conception bnl I , 

(15) Brand of conception bull, 

(16) Services par conception. 

(17) Oeu of partorlclon. 

(19) Birth weight of calf, 

( 20 ) Beprodoct] ve disorder. 

above, the following Information was considered 
lactations studied. 

(9) bactatlon nuater. 

(10) Date of parturition. 

(11) Age at parturition, 

(12) Days dry before this parturition. 

(13) Laogth of lactation. 

(16) Hi Ik production. 

(13) Fat peroantaga, 

(17) Cause of and of lactation. 


lied on the actuoT aervleoi fer donceptlon, 1 
a cransForiBatlon of the dejMndent verTeble wi 
■ iquaro root treneforaatian wae enployad. T 

transPomatlon xas perforind due to the fact thot the nutrhar of 
services per eotiception does not follow a noriaal dlstrlbiitTon. 

calculated by using the teost-squares estimators for components of 

and k; was calculated by the rormula 

total nunber of observations. 


]n calculating the atendard arnors of the herlteblllty oatlmatas, 
the formuTa given by Swiger at a), was used. 

) ■-* 

I. (Ol, C crl^ , <r|j, 

(®s. • CTs . cr| ) » (drf , o? ) 

:re: 0-1 ai cri 

pooled) .~l.\y 2 (n. -I) (l-t) pa(X-l).3^ 

(n,-S) (S-l) 






It ytelil ani Iflt fat ccrroetsd milk (kS FC«) . Tba formgla usad 
invert mi Ik yield to k% FCH was that suggested by Ualnes (84): 

year, tenth and sire. For analysis of first 

Covnriatos Included wore linear and quadratic cooponants For 

cubic comoonent of age was added. To Improve the inverse, the 
covarlaiss ware adjusted by subtracting constants as follows: 

If heifers nature cows nij_ 

days open (DO) 
Provlows dry pt 

.^1 > ^yh *< 7 ^ 

O’! H th5 Sira « 

'J’C Is Oi. c~co. 

.wltMnF^, . HS. 
:e »f cows {<rh was a- 


-.-\/var (O?) 

of * Cr* * Oh 

EtciMCes oF psoled Pwr IKbl 1 1 list Including data aF [he throe 
hards togalhsr wore colculoud hy using ttio Fornulo as followsi 


*• K.i.jl *• <='2, .2,,' 

Hhero: <y|| ^ ^ Is tho siiai of the siro varTanees In ftordi I, 
and 3. Hopaatabl 1 1 tias wars calculated by a slmMar approach, 

Pooleif repoatabl lUIes estlmaEas were calculated by using sanB 
formula employed was as follotre: 

In oscTmactng standard errors for pooled repeatobl 1 1 ties the 
following formula was utilized: 

) (I - «pl^ [l '■[Kp -!)»,,] ^ 
• (I-nv. -Ell) (En-I) 

A further analysis was doslgned to ostinate herd by sire Inter- 
action, using 1(56 records from 203 daughUrs of 20 dlfforant sires 


used In ertlflcUl Insemination ae well as In natural service In Che 
three herds, Data Included wera the adjusted responses. Adjustment 
Mas based on the leasl-sitaaros coefficlants estimated In the analysis 

Independent variables taken Into account In the aiadol uere: 

In tha analysis oF the group of ell cows and previously teantloned. 
end hard by elre differences were eelcuieted. The corresponding 

•d (fined) CTI * ChS ♦ K " 

•e (random) ®*R + K o\ 




For ooniMrl3«fl percontogoo of Cocol vorTsnco wero oloo calculoceO 


J, gj 

5 5 

*'■'1 i Htm » 

563 7.02I1 

99 6,967 13k 11.059 

canC for any of Eha herd!. These rfleulta dtsa^rea with those ob- 
tallied by Alin (b) and by Shardo at al. (172) In their studies with 

InCra-herd hnritablllty astlnatae for calving Intervals as 
reported In Table 4, were -0,05, -0-15. and TO. 17, respectively , for 

lability estlnates found can doubtless be attributed Co sampling 
error so the her! tabi 1 1 ty of calving Interval Is considered from 

results agree with 0 value' 
breeds In tropical areas. 

However, results In 

r.vs, was 53 days as reported by Bud 

la (Sb), In reproductlvB abnormal cows; 
in seven years old as Indicated by Hersian 

However. th« rosultj are «»ra in agreamint with die ioMrval 
obtatned by Hirt (94) oF 83.5 daya Fron Spotcod Hountoln cattle ia 
Scraiaay and with those reported fro* tropical areas by Oessouky and 
Rokko (66) of 85.52 days In Holstein cattle In £gypt, and 8? days 
obsorved by Hies Ft I ho and Costa Aroei ra (I36) In Gl r dal ry cattle 

labia 5 shows the least-squares analysis oF variance for calving 

heat ware highly significant (p <o,0I) for Herds I and J, and signif- 
icant (peg. 05) For Herd 2. 

The effect oF month was not slgnlFlcant In any of the herds. 

In most oF the literature reviewed, the effect of iionlh was not 
anelyced; however, Carman (48) found that days to first estrus varied 
marlcedly from month to aonth. The highest huidjor of days to first 
estrus was for those calving In rtarch, the minimum In Septambsr. In 
some studies. It was found that season of calving had a significant 
effact upon the interval between calving dote and first heat, Shorter 
Intarvols for cows ealving during suimr wora observed by luch et el. 

■a (S6) 

Sire affects were not significant for Hards I ainl 3, bm were 
SlgnlFlcant (P<0,0$) In Hard 2, 

The affect of age of cow was not sign I FI cant. These rasul ts ware 

Indicated that FIr.t calf heifers had shorter intervals then cows up 
to 7 years old. Age of cow also Influenced the Interval from parcuri- 

Toble 6. 



gstfMted vali>9 for th« pooled harttabnity ovorall avopego for i 
three herds together was -0,02. 

Ho reported Inforieatlon coacorned with the letorval from fli 
Heat to first service was ivaiteble, so that a comparison with th 

s almost completely determined by ovtnagement 
'ble was inetddod mostly for the saU of eomplately 

First Service to Conc octlo a 

In tomparato coontrlos whici 
{48} to 52 days by Poo et a1 
from tropical countries, 
year effects on the Int 
os presented In Teble 7, wet 

wl th exception of age I Inoer i 

-a effects ware reported by Tabler 

■I. (IBS) 

•ffActs Of a^e 

found CO be 0.52, 0.11, and O.OS, rospocCWoly, The pooled herl ce- 
bfliCy valuo was 0.08, Table b shows a sunnary of herl tabi II ties 
and standard errors for the variable studied, Tho pooled horUabllity 
value of 0.08 Is eomparablo lo tho 0.07 eslltnetod by fou st el. (153). 
Smaller herltablllty estimates for tho same Interval were reported 
by Carmen (48) and Dunbar and Henderson (70). 

1,7. Those results, in general, are closely In agreement with Chose 

by Tanabe end Salisbury (ISf). 

On the other hand, results obtained In this study are different 
than theta obsorved in studies with European cattle performing In 
tropical araas, such as tho values of 3,3 and 2.3 reported by doubert 

1105) from study with Holstein heifers In South AFrioe, or the 5.64 
services per conception for Holstein cows In Breeil Indiceted by 
Cerno end datlste (45) end the observed services per conception of 

services per conception, orlglne] end tnensformod dote. Veers hod e 
highly significant effect {Pe.OI) In the three herds with exception 
of Herd 2 In which the effect wes stgelflcent (P < .05) when trees* 

IS highly si gni f- 

slgnlflcanee (P <.05) in Herd 5 end a 

transforioad dace the veiues were 0.04, 0, end 0.17. Ulth exception 
of Che nerltability values observed In Herd 3 of 0.15 end 0,17 for 

agreement with near to zero her] cebil I ties found by Legates (US). 
Carman (48), and other Investigators, such es Singh (173) who 
reported a her! tabi II ty value of -0.048 in study with Thsrparkor cows 
In India. 7he pooled hsri tab! II ties fon the three herds together were 

The low herltebllity estimates obcelned for the variables celvlnf 

concapclon Cor[gtr>al ^ 

conception {transFortwd data). 

ervicss per conception .which ere boltevcd to Tnfloenco 
•ervIcB period ami eomoquontly tho calving interval Inillcatc 

if roproOiictlvo afficloncy, 

ly nanagamnt 

pollclas rather than genetic influences. Consoquontly. improvaO 
iKanageeient systems most ha emphastjed in order to obtain an optimal 
calving Interval. This fact Is of particcilar Importance in the 
Tmprovoment of dairy cattle In tropical areas. One of the comwn 
reasons for longer calving Intervals, which Is typical In many 
European dairy cattle herds In tropical countries. Is tho relatively 
low level of manegenent to which many of those herds are subjoetod. 

The lengths of calving Intervals ohsarved under the conditions 
of this study could be explained on basis of tho gradual Improved 
monagament that has bean applied to those herds through the years, 
Sostatl on Lennth 

Table 2 indicatos roans and standard errors for gestation length. 
Tho gestation periods were quite similar for tho throe herds being 
280, 273, and 281 days, respactivoly. 
agraament with results from Holstoln ct 
countries which has been obsoi-yed to v; 

iso findings w* 
la studied In I 

Similar gestation pc 

Is of Holstein cihvs undt 
ry ranged from 276 days 
o 282.8 days Found by v 

by During C7I). 
as Indicated by Volga 

presented in Tsdlo 10. Mo sisnifTeent effects of • 
Unfortunately lleUe inforoatfon In the literature 
effect of year on oestetlon length. Host results i 
the effect of season and/or eontti of year and thest 
rather conflicting. 

Hoaever, sire affected sign! flcently £P e.05) 
significantly (P e.QI) the gestation length In each 

Knott (log) sieied the poasIbllUy of paternal Influence on gestation 
Icnglh, and Aleaander (5) Indicated tl 
the satie Interval, Significant effects of si 
have been also observed with native breeds 
ever, Briquet and Abrau (42) from analysis 1 

Influencad significantly by sire. 

No Influence of aga of dam on gestation length was observed. 
These findings are similar 10 the results of some in.eillgetlons from 
teoporete countries, such as those reported by Copeland (59), and 
Davis et al. (60). The same conclusion was indicated by Investigators 
of native breeds In tropical regions st 
Singh et el. (177) end Joufaert and Boosna (106), 

ot el. £40) . Herjnan et el , (91) , and Stallcup ct 
that the age of cha dan iffacts the length of th 

in gestation periods 
n tropleel areas. Now- 
'f data of nllltlng Zebu 
>e gestation period was not 

gestation period 

t-squams analyale 

rejjortcd studios of gostatlon 

varionco for birth woTgfit. Highly sign! fT can t effects (P «.0I) of 
year were observed In Herds I end 3 , while no significant effect was 
dotoeted In Hard studies of Tyler el at. (192) and Martin (I3J) 

ferancea between years In tl.alr studios wllli HuNtolu. In HIsooiisIm 
and lowe, respectively. 

Konlh of year was found to have highly significant affects 
{f <.QI) on birth weight of calves on IJnnf I. This result agrees 
with clroso obtained by Juina and Itasslr (10/) froia a study with Holeteln 
cattle and by bhal la at al. (30) from dahlwal data. However, sevoral 

C-squares analysis 

Kagab (20), Anantabrlshnam 

(ro), Tyl»r at al. (IS2) and Martin (132) ha.e Indicatad that nonth 
of calving and/or season of the year have Hctte or no effect on 
birth weight of tho calves. 

( 13 ) goes 

VOS showed a highly significant (f<,QI) effect on 
calves In Herds T and 3. These results are In agree- 
eported results of various authors Indicating that, In 

m to be of Importance within the Holstein breed in 
In birth weights ss reported by Andersen end Plum 

weight of the celvos was not signi flcent ly affected by so*. These 
findings are In accord with the same results observed by Jumo and 

A significant effect of sire tPc.OS) was foun 

herd was vary closo to being significant at the 5 % 
enee of sire on birth weight has been reported also 
Investigators among thorn Fitch el al. (81), Footo e 
Aoy and Goswaml ( 16 $). 

Host Investigators anelyelng dairy data have ol 

Those positive correlations ranged between 0.25 to ( 
In this study gestation length hod no signifloaot el 
weight In Herds I and 3. This Is In agreoinent with 

Uiat Irrficatod that Cha eorrelattoa hatwsen birth Kolght am) g«ta- 
Clon leitgtli is vary small or doas not exist. Atysng these studies 
are those reported by Echles (72), McCandnsh (I3I») end FI tch at al. 

(81), Kowover, It Is iraportant to mention that the above three 

tropical as Mall as teoiporacc zones. 

three herds, respectively, 

Blacknore et al. (31). Tyler 
Homan et el. (I6b), 

t have studied the herltablllcy oF birth 
Fact, horltablllty estimates varying 
reported by Legault and Touchberry (IIB) 
at el. (192), Asker and Aagab (10), and 

disposal. Approilmatcly S5X were sold and 15* died. 

tiva percontaaos Is presented In Table 12. The main reason for disposal 
In the present study tvas lorn roproduetlon at Mt, I16, and 3SS for Hards 
I , 2 and 3. respectively. The pooled value for the throe herds mas 

llEorature vihlati ranged From 7% ae reported by Seach (I 7 I) to 33 * 
ai Found by Salazar (167). Houever, Ft Fa important to mention that 
ttiB prtncfpai reeaon for diapoaal reported by ntoat auttiora inciudad 
In the review of Itteraluro woa low production and not low breeding 

efFIcIcnoy. The pooled value of bl* found In thia atudy wea In 
agreenttnt with the eatlmate obtained by Parker et al. (Ib 7 ) who 
reported 41* of diapoaala due to low reproduction. Ki^ parcontagea 
for low reproduction found In the preaent atudy might be parclalty 
explained by the aouroaa of the data atudled. Special care of 

exparliaenlol harda and the oowa aro culled aoon after breeding 
difficulties are prasant. On tha contrary, moat studlaa mentioned 

>r example, often would cc 

by tba relatively desih loss (27%] wblch limits the nuirter oF 

IricTudad Ir 

production oF tbe cows culled may not be satIsFeecory for the mlnieum 
milk production re^ulrod To the experimental herds, but provide 
enough production For the standards of the commercial ml Ik producers, 

age, miscellaneous, accident, and mastitis were classified in one 
category which accounted for 10% oF the disposals. The value observed 
in Hero 1 was 6% while In Herd 3 Che percentage was 22- Ko Information 

guently, Che value of 2% corresponded only to mestltls. The higher 

the relatively low valve observed In Herd 2 could be explained on Che 
highor percentages for cows culled for age (10%), miscellaneous (St), 
end accident (5S) in contrast with the values of 3%, 2S. end IX found 

Mins 13* and 13*, nejMclivoly. Ko*ev«r, a mueii higher percentage 
(27*) of cons died in Herd 2- A possible explanation of this finding 
could be that the (rue tropical condUiona exlatlng In Station 2 xlth 
more edvoree clioetic effects, have affected more drastically the group 

and parasites Is present, Table 12 sho.s the high percentage {IK*) of 
death due to heeeparesl tes, contributing to Che o.crall high death 
losses In this herd, Death due Co hatroparasi tes such as enaplasnia, 
babesla, and piroplesma la consEon in cattle under tropical conditions 
end occurs mainly in European cattle subjected to this type of enulron- 

lift and respectiuelv. The major 
abortion and bioat with a combined v, 
Beoeuse the Infoneatlon on reasc 

hemoparesltes and a 

or disposal and nalniy th 

in general, the results in the present study suggest the emphasis 
that have been paid in the three herds to reproductive problems. This 
is reflected in the high percentage of culling found for iou reproduc- 

sn for miloi, Itn for 

find l.iiTX for iTBiltIpIfl births was 

Ihori the Krcentage of 
sssfin {99], and eomparod 
El-ltrlby (17), 

data from tdrich Johansson (99) 
tha discrepancy of tha results. 


and Wt PCK yields from fl 

holfors, moture cows and all cows. 

Avoraje milk and tat yields for all cows ranged from 3,1|S3 and 
124 kg 10 4,506 and I53 kg, respeotlvoly. These yields ware In the 
range observed In uperimental Holstein herds In tropical regions. 

be expleinftd by the 
C0M9 frote hoi lend. 

fepent genetic beckgrocnds of the origine] 
d 3 wes formed originally with groups of pun 

to 47 In the Appandlm present mean yields end least-squares coefficients 

Since in the analyses of mature cows the variable previous dry period 
was considered, only records with this Information were included in 
this group of cows, however, when all cows were studied previous 
dry period was not Included In the model, Consequencly soma records 
not considered In analyses of mature cows were Included In me all 

elgnlfloantly (f e.DI) in Herds 1 end 3. However In Herd 2 this 

least squares analyses showed no significant affect of month of 
ceTvIng upon yield In herd 3. On the other hand, significant affects 
(Pe.OI) wore found in the other two herds. Conflicting results have 

s, Verletlon 

5 « 

n«ril I Herd t _ Hard 3. 




Tablo 20, LcflsE'StiLiaras analysia of 




1/1 yield with BOnth oF calving mss not slgnlficanc l/i several 
studies {39, III. 121. 125. 170. 175, 199). On the other hand. 
slgnUlcent differences have bn reported by other Investigators 

surprising since cllisete varies enong the different areas. Weosurlng 
the effects certainly has value In every study to help describe and 
charactorlte the data and to avoid nehlng poor ostrnotes of otbor 

faak production ives attained 

in agrooflunt wl th tl 

r tropical conditions. 

highly signi Flcant 

agroe wl Eh m 

i 2, On ths oEher hand, aga significantly Tnflucrtcod 
3 COWS and cot^incd groapa. In gandral thsae resulU 
studies In EetnperaEe as wall as EropTcnl areas, 

Ag« correcllan factors oars nstlinaled with the sOjectlvn of 
gaining knowledge on differences betwaen correction factors calcu- 
lated In temperatn countrlos as coiepared with tbosa obtained under 
tropical condl lions. Ills important to emphasize that If di fferencos 

■n factors between cattle of tomperole and tropical countries 

incorrect to use conversion factors ft 
Consegucncly, correction factors she 
ea to which they are applied. 

je obtained 

Included In this study, Che accuracy ol 
ever, this preilrilnary Information coul 

were calculated separately for each hoi 
In stetiscicei procedures. 

Table 48 of the Appandli shows tht 
in this study. In general tho factors obtained era gulta simih 
those found for Holstein cows undsr tomperete conditions, SInct 

tompsrale countries, It Is suggested that the latter centinue tc 

reali»tTc figures 

not possible t 
Holstein catti 

bays. These figures are In agreeirenc with 
;l-ltrlby end Asker ( 73 ) In Igypt. 

Mehadevan {135] Indicated cl 

id with 5% reported by Hehadevan (125) I 

lord signi f f cently 

itlon length has been foi 

reported by nphadevbn (126) Co 0.9 oceordln^ Co Nsido and Oasai (I3B). 
Vanda (199) ahowad Chat linaar and quadratic affects of iangth of 
record on ailik yield «oa aca tiecical ly significant In pure and crose- 

2, 102, 179), ParCIculerly, long parlode eera obi 

aacli nerd, Parcantagas of 12, 18 and 21 »ere obs 

raa hands had lass chan SO days open. 

Pasulcs of analyses tTafales IS to 2tf) shonad th 

ys open significantly In- 
, contradictory results were 

were In agreement with tha significant el 
yield of dersey cons In Florida repontad 

suggest a need for Further Investigation 

< earrantes (22) . 

Tabic 26 . Analyiic oF variance For producClon data oF all cows 
odjuated for all significant eFfacts except for sire. 

separatfily vary widely 

eofablned [Table 25). 

A possible explanation could be 
InFlatlon of sire variances due to 

cically high Bvon after discounting ehcm somrdiat in view of sitable 
standard errors, The discrepancy berwacn these estlaetes and 
reoeatabl I i ty estimates shown In Table 2B llltewisa suggests that sire 
variances reflected effects other than the breeding value of sires, 
or that genotlc differences between cows for some reason were much 

Considering all possibl I it 

epperencly Inflated sire variances 
ons resulting from 
non-adjustable confounding of sire 

of sires to which dams wore tnotod was not entirely a matter of chance; 
or 3) unusuoTly distinct differences In genotypes due to the wide 

Acpual abI 1 i tv 

fstiinetes of ropcetabll I ty of lactation records by Intre-clnss 

Kilk yield 0,S?*O.D6 0.32 ^ 0.07 0,41 t 0.08 0.31^0.04 

eorrelacfans oF adjusted records oF s]l cows are preserccd id Table 
28. Is shows a sumarv of wT thin-herd and pooled repeacabi 1 1 Cios 
calculated by using fontajias IndTcacad in statistical procedures. 

WIthIn-herd repeatability values For lactetTon yields showad 
the same wide variation that v/as observed In Fieri tablllty estimates 
already rcentloned. Values ranging from -0,03 to O.iil wera observed. 

yields, respectively. TIse unusually low value For Fat and 
yields as compered with that for milk yield Is surprising I 
the part-whole relationship between the different raasurcs 
tion. ItepsatabI 1 1 ties obtained From thaso data In general 
the lowest oF those given in the litereture from temperate 
which average appronlmately 0,30, However, repeetebl 1 1 ties 

121, Il*l, 179) In tropical areas which vary From 0,31 to 0,6S. 

partially explain tha contradictory results observed. 

ita analyzed Ft 

y ccnsistdd of 4g6 records 

vice, Date Included were the 
a coofflcients estimated in 
study were considered only 

Av. dAughtar pc 

nilk^leld <kg) 
Fat yield (kg) 

difFerences anong paternal 

Sire by herd TnteraccTdn aff 

mik yield 


It yield 


fitting of 


production levels (133, 161). under different manapeteenc systems 
(UK, 133), end IF daughters of dulls have been artificially or non- 
ercIFicIally bred (201). Finally a broader regional espect of such 
interactions has been recently considered (120) and evidence Indicated 

The highly significant herd b| 
data could be explained In Lmo way: 

.hat the {nfferences were i 

Ic differences be 

by a widely divergent origin of sires; 2) 

variations In production levels In the thi 
and managerial conditions, and by obvious 
Che locations of the herds. 

The possibility of genuine llcnitatlons existing it 
has been indicated. The magnitude of the Interactions 
over must be Interpreted as being suggestive of a real 
The widely accepted use of semah from temparate countries to 
inseminate dairy cattle In tropical areas emphasises the In^ortance 
of gaining Knowledge about the contribution of genotype by onvlron- 
mentel Interactions. It Is suggested that some attention to these 



GeiTotlc and envtranraanCat Factors sFFacting raprodi;ctTv« and 
The data analyzed covered the period from 1956 to 1967. Sons 1,390 

services per conception, gestation length and birth eelght wore 

iverall moans For calving Interval varied From 419 to 436 days. 
Intervals nero close to the optimal limit oF 14 noeths reported 
idles from temperate covntrics. For the sake oF describing 

3, rospectlvelv pvere: For calving date to First heat, 66 , 63. 

IS highly slgnlfloanc 


b pcbibd herltbbnicy eicimites rented from 

Overall means for gestation period ranged from 27d to 261 dj 
bo ilgnificant effects of year or age of cow were observed, How< 
significant effects of sire In die tliree herds were delected. Ti 
pooled her] tebi 1 ity was 0.2B, 

Variation In calving interval 

by genetic causes. This is confirmed by the heriteblllcy estimates 

whereas moderate estliretes were found for gestetlor length. These 

r^lnieln e high reoroductlve effloienoy In Holstein csttle subjecied 
« three different environments Included in 

ritflbUttv esclritea ranged 

rasciLfs wer« i 
difFirent eai 

t For cow disposal word low rcproducclon wrticli 
oF disposals In the three herds. Uw prodiietlon 

!re also principal caiisas for culling with 3i| and ICP* of 
respeccWely, Approxlisately ISX of the cows died for 

'N percentage oF cull Ing ft 

Fror> 1,365 calvings studled'a sex ratio of 53% For siales, and 
•*re for fetneles, and I.47S For siultlple births, was obtained, 

fffects of age, length of record, days open, previous dry period, 
year and tronth of calving, and sire upon milk yield, fat yield, and 

milk yield, fat yield, and Ift FCH ranged between 2,910 and 3,872; 103 
and 134; and 2,693 and 3,568 kg, respecelvely, Hature cows averaged 
68 months, 296, 175, and g8 days, for ago, length of record, days 
open, and privipus dry period, respacllvely. Average milk yield for 
this group of cows varied frcn 3,685 to 4,885 kg. 

In general, analyses Indicated that ago significantly affected 
yields of mature and all cows, effects of age on first calf heifers 

maturl ty 

iffect slgnTflcocIvely ml Ik production, Hw~ 
*, controdIcEory results Mere found for foe end FCH yields. 

letect e slgnlfloont effect of previous dry 

then 40 days could explain these results, 

herUablllty end ropeatebinty estimates. Pooled harlceblllty values 
ware 0,31, 0,08 aod 0,13, respectively, Umltatlen In nunber of 

and unusual differences In genotypes of sires represented we 
high herUablllty ostlieates ooservod, A small volume of dal 

sire sign! f lea tl voly effected ml Ik, fat, end 4% FCH yields with 

suppartod by 

faMurp to agrot Mith inost otbar studias wharo 
jy Sira interactions have bean detoctad might ba 

re Interactions observod suggastad that attention 

itudlad indicated that good reproductive officlQncy and sacIsFaccory 
can be used successfully to increoso milk yield in the three regions 







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s:sN. S; rs,;-;:::. 


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«Us Fllhg, A, , and J, A, 0. Costa Aroelra. 1SS5. The Interval 


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20S. Ullcox, C. J., and J. A. Staffa. I96A, Effects of uterine 
horn pregnant, age of dam and sea of calf on birth weights 
and gestation lengths of dairy cattle. CAbst.], J, Dairy 

209. Wllcoa, C. J., and H. V. Young. 1962. Effect of season and 

yean of freshening on ml Ik production. Fla. Agr. Enp. Sla. , 
Dairy Ecfence KTmeo Report 63'3. 


Juan Jose Selsier C. was boro in Anserna (Csidos). Colombie, on 
March 24, |q}5. in Hoveober, 19S3. *>« w»o gradusted from San 
Bariolorns (u Kercad) High School at Sogota, Colombia. In Oacanber, 

Infantry in Bogota. In I96I, ha racelvad the dagraa of Bachelor of 
Veterinary Medicine and Animal Hesbandry from the national University 
at Bogota. In his senior year he was sleeted student president of 
his college. In this capacity he served as reorosentatlve of the 
Veterinary Medicine School on the National University Student Body 
from I960 to 1961. 

Following graduation, he enrolled as Anltnal Science researcher 
In the National Dairy Program at cite Colombian Agricultural Institute 

In Septembar, I963, he entered Graduate School at North Carolina 
State University. In 1966 he was granted the dagnee of Master of 
Sclonoe. In September. 1967, he enrolled at the University of Florida 
and has been working towards the degree of Doctor of Philosophy. 

He Is a menber of the Colombian Soolety of Veterinary Medicine; 
he Is also a charter leember and was first president of the Colombldn 
Assodlation of Animal Production. At the present time he belongs to 
the Board of Directors of the Utin Aiiarlcan Association of Animal 
Production. He Is also i nember of the American Dolry Bclance 

Association, and Che AmerUan Society of Animal Science, Uh 
Ing Che LInIversity of Florida, he was elected to meetershlg 

chalman of eandidi 
DBBn of chB CoHbsb of Agriculture end to the GrsduBte Council, > 
degree of Doctor of PMIosophy, 

me, 1970 

Dean, Col lege ' 

/ tr 

a C